Three dimensionally interconnected module assembly

ABSTRACT

A method and apparatus for interconnecting electronic circuits using nearly pure soft annealed gold mechanically compressed within through-plated holes. The invention has its application in attaching integrated circuit dice directly to circuit boards by ball bonding gold wires to the bonding pads of the integrated circuit dice in a substantially perpendicular relationship to the surfaces of the disc and inserting the gold leads into through-plated holes of circuit boards which provide an electrical and a mechanical connection once the leads are compressed within the through-plated holes. The present invention also finds its application in the interconnection of sandwiched circuit board assemblies where soft gold lead wires are inserted into axially aligned through-plated holes of the circuit boards and compressed so that the gold lead wires compress and buckle within the through-plated holes, forming an electrical connection between the circuit boards.

This is a continuation of application Ser. No. 07/053,142, filed May 21,1987.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the field of electrical circuitinterconnect, and more specifically to a new apparatus and method forhigh-density packing and interconnect of integrated circuits on printedcircuit (PC) boards and PC boards on PC boards.

BACKGROUND OF THE INVENTION

Integrated circuits are typically fabricated on wafers which are cutinto individual integrated circuits and packaged within hermeticallysealed ceramic or plastic packages. The signal and power lines from theintegrated circuit are brought out to the pins of the package by meansof leads attached to the bonding pads on the integrated circuit chips.The chips are then used to form larger circuits by interconnecting theintegrated circuit packages by means of PC boards. The circuit boardscontain interconnect lines or foils on the surfaces of the circuitboards or within planar layers. The circuit board is populated withintegrated circuit packages which are soldered to plated via holes or onsurface mounted pads on the circuit board. The soldering process formsan electrical and mechanical connection between the integrated circuitpackage and the circuit board.

To form larger circuits, circuit boards populated with integratedcircuit packages are interconnected by a variety of connectors, jumperwires, or cables. The physical arrangement of the circuit boards inrelation to one another is also accomplished in a wide variety ofconfigurations. One popular high-density interconnect technique is tostack the circuit boards in a sandwiched relationship to one another andelectrically interconnect the circuit boards with interboard connectors.This packing technique achieves a fair amount of packing density,limited by the interboard spacing requirements of heat dissipation andconnector spacing.

The aforementioned technique of forming larger circuits from individualintegrated circuits using integrated circuit packages and circuit boardsresults in limited packing density of the actual area which is used forelectrical circuits. The actual integrated circuit chips themselves aretypically smaller than one-tenth of a square inch, and in total wouldcover only 10-20 percent of the board area. However, due to theinefficiencies of packaging of integrated circuit chips and connectingthe integrated circuit chips to the circuit boards, it is difficult orimpossible to increase the packing density on circuit boards to improvespeed or spacing advantages. In addition, inter-board spacing is limitedby the area consumed by the integrated circuit packages and inter-boardconnects. This limited packing density limits the inter-circuit signalspeed due to the long propagation delays along the long interconnectlines.

The present invention provides a new apparatus and method forhigh-density interconnect of integrated circuit chips on circuit boardsand between circuit boards which overcomes the wasted space and speeddisadvantages of the prior art.

SUMMARY OF THE INVENTION

The present invention provides for placing unpackaged integrated circuitchips directly on circuit boards by using soft gold lead wires attachedto the bonding pads to form the mechanical and electrical connectionbetween the integrated circuit chips and the circuit boards. The presentinvention also provides for interconnection of sandwiched circuit boardsby using soft gold jumper wires connected through the through-platedholes of the circuit boards.

Gold wires comprising nearly pure soft annealed gold are ball-bonded tothe bonding pads of integrated circuit chips, and the soft gold wiresare stretched to a substantially perpendicular position with respect tothe surface of the integrated circuit chip, forming flying leads. Thecircuit boards to which the integrated circuit chips are to be attachedare manufactured with plated holes having hole patterns substantiallymatching the bonding pad patterns of the integrated circuit chips. Theintegrated circuit chips with the flying leads are then positionedfacing the circuit board and the flying leads are inserted through theplated holes such that the flying leads partially protrude from thecircuit board. Caul plates are then positioned on the outer sides ofthis sandwich and pressed together so that the sticky or soft gold ofthe flying leads is compressed within the plated holes, causing the softgold to deform against the surface of the plated holes and therebyforming a strong electrical and mechanical bond. The caul plates arethen removed and the integrated circuit package remains firmly attachedto the circuit board. This results in improved packing density ofintegrated circuit chips on circuit boards.

Gold wires comprising nearly pure soft annealed gold are insertedthrough axially aligned plated holes of two or more circuit boards in asubstantially perpendicular direction to the planar surface of theboards. The gold wire is selected to be slightly longer than thedistance through the axially aligned holes such that a portion of thewires protrude through one or both sides of the sandwich of circuitboards. Caul plates are then placed on the outer sides of the circuitboard sandwich and pressed together so that the soft gold is compressedwithin the plated holes, causing the soft gold to deform against theinner surface of the plated holes to form an electrical connectionbetween the circuit boards.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, where like numerals identify like components throughoutthe several views,

FIG. 1 is a side view of an integrated circuit die onto which flyinggold leads are ball bonded and straightened by a ball bonding machine.

FIG. 2 shows the six steps that the flying lead ball bonder performs inorder to attach a flying lead to an integrated circuit die.

FIG. 3 shows the bonding pad pattern on a typical integrated circuitalong with the corresponding plated hole pattern on a circuit boardwhich mates the integrated circuit chip to the circuit board.

FIG. 4 shows the relative positions of the integrated circuit chip andthe circuit board prior to compression of the flying leads into theplated holes.

FIG. 4a is a closeup view of a single ball-bonded flying lead prior tocompression within the plated hole of the circuit board.

FIG. 5 shows the relative positions of the integrated circuit chip andthe circuit board after the flying leads have been compressed inside theplated holes of the circuit board.

FIG. 5a is a closeup view of a ball-bonded flying lead that has beencompressed into a plated hole on the circuit board.

FIG. 6 is a larger view of the compression process whereby a pluralityof integrated circuit chips having flying leads are attached to a singleprinted circuit board through the application of seating force on caulplates which sandwich the circuit board/chip combination.

FIG. 7 is a plated hole pattern for a typical PC board onto whichintegrated circuit dice are attached in the preferred embodiment of thepresent invention.

FIG. 8 is a module assembly onto which a plurality of circuit boardspopulated with integrated circuit chips are placed.

FIG. 9 is a side view of the module assembly of FIG. 8 showing thedetails of the logic jumpers and power jumpers for logic and powerinterconnection between the sandwich assembly of printed circuit boards.

FIG. 10 is closeup view of a single logic jumper that has beencompressed within the axially aligned plated holes of the sandwichedprinted circuit boards of the module assembly of FIG. 9.

FIG. 11 shows the first two steps of the pressing operation forcompressing the logic jumpers in a single stack assembly of PC boards ona module assembly.

FIG. 12 shows the second two steps of the compression of the logicjumpers on a single stack assembly of four printed circuit boards on amodule assembly.

FIG. 13 shows the method of compressing the power jumpers through theassembly of stacked printed circuit boards.

FIG. 14 shows the compression of the gold posts between the power platesand the power blades of the module assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment of the present invention relates to thehigh-density packing of silicon or gallium arsenide (GaAs) integratedcircuit chips on single-layer or multi-layer interconnect printedcircuit boards with plated-through via holes and the high-densitypacking of circuit boards in a sandwiched arrangement. The applicationof this technology is designed for speed improvements, improved heatdissipation, and improved packing density required for modernsupercomputers such as the Cray-3 manufactured by the assignee of thepresent invention.

The placing of the integrated circuit chips or dice directly on thecircuit boards eliminates the bulky packaging normally found onintegrated circuits and typically referred to as DIPs (dual inlinepackages), SIPs (single inline packages), SMDs (surface mount devices),leadless chip carriers, and the like. All of the aforementioned packagesconsume valuable circuit board real estate and in turn cause increasedpropagation delay between active circuits due to long signal paths. Inaddition, the aforementioned circuits present heat dissipation barrierswhich vary with the thermal conductivity of the packaging material. Byremoving the chips from the packages and placing them directly on thecircuit boards, the integrated circuit chips or dice can be surroundedby liquid coolant to improve cooling.

Flying Lead Construction

FIG. 1 shows the preferred embodiment for attaching the flying goldleads to the silicon or gallium arsenide packaged chip or die beforeattaching the die to the circuit board. The leads are made of soft goldwire which is approximately 3 mils in diameter. The GaAs chips used inthe preferred embodiment contain 52 bonding pads which have a sputteredsoft gold finish. The objective of the die bonding operation is to forma gold-to-gold bond between the wire and the pad. A Hughes automaticthermosonic (gold wire) ball bonding machine Model 2460-II is modifiedin the preferred embodiment to perform this operation, and is availablefrom Hughes Tool Company, Los Angeles, Calif. This machine was designedand normally used to make pad-to-lead frame connections in IC packagesand has been modified to perform the steps of flying lead bonding asdescribed below. The modifications include hardware and software changesto allow feeding, flaming off, bonding and breaking heavy gauge goldbonding wire (up to 0.0030 dia. Au wire).

The Hughes automatic ball bonding machine has an X-Y positioning bedwhich is used to position the die for bonding. The die is loaded on thebed in a heated vacuum fixture which holds up to 16 dice. The Hughesbonding machine is equipped with a vision system which can recognize thedie patterns without human intervention and position each bonding padfor processing. An angular correction as well as an X-Y position isavailable to the machine.

The soft gold wire that is used for the flying leads in the preferredembodiment of the present invention is sometimes referred to as stickygold or tacky gold. This gold bonding wire is formed from a 99.99%high-purity annealed gold. The process of annealing the high-purity goldresults in a high elongation (20-25% stabilized and annealed), lowtensile strength (3.0 mil., 50 gr. min.) gold wire which is dead soft.The wire composition (99.99% pure Au non-Beryllium doped) is as follows:

    ______________________________________                                        Gold                  99.990% min.                                            Beryllium              0.002% max.                                            Copper                 0.004% max.                                            Other Impurities (each)                                                                              0.003% max.                                            Total All Impurities   0.010% max.                                            ______________________________________                                    

This type of gold is available from Hydrostatics (HTX grade) orequivalent.

Referring to FIG. 1, the flying lead die bonding procedure begins withthe forming of a soft gold ball at the tip of the gold wire. The wire isfed from a supply spool (not shown) through a nitrogen-filled tube 109(shown in FIG. 2) to a ceramic capillary 100. The inside of thecapillary is just slightly larger than the wire diameter. The nitrogenin the connecting tube 109 can be driven either toward the capillary oraway from the capillary toward the supply spool. This allows the goldwire to be fed or withdrawn from the capillary tip.

The gold ball 106 formed at the end of the gold wire 101 isthermosonically bonded to bonding pad 105 of chip 104. The capillary tip102 of capillary 100 is capable of heating the ball bond to 300° C.concurrent with pressing the ball 106 onto the pad 105 and sonicallyvibrating the connection until a strong electrical and mechanicalconnection is formed. The capillary 100 is then withdrawn from thesurface of the die 104 and the wire 101 is extruded from the tip 102. Anotching mechanism, added to the Hughes ball bonder to perform thespecific notching operation described herein, is used to make a notch107 at the appropriate height of the flying lead to break the connectionand to stiffen the lead. Wire clamp 108 grasps the gold wire 101 and thecapillary is withdrawn upward, breaking the flying lead at 107 andconcurrently performing a nondestructive test of the ball bond tobonding pad connection.

The sequence of steps required to make a flying lead bond to the packagedie is shown in FIG. 2. Step 1 begins with the feeding of apredetermined amount of wire through the capillary 100. A mechanical armthen positions an electrode 114 below the capillary tip 102 and ahigh-voltage electrical current forms an arc which melts the wire andforms a gold ball with a diameter of approximately 6 mils. This istermed electrostatic flame-off (EFO). Specified ball size range isattainable through EFO power supply output adjustment up to 10milliamps. During this step, the clamps 108 are closed and the nitrogendrag is off. This action occurs above the surface of the integratedcircuit chip so as to avoid any damage to the chip during the EFO ballforming process.

In step 2, the nitrogen drag 109 withdraws the supply wire 101 into thecapillary 100 and tightens the ball against the capillary tip 102.

The capillary tip 102 is heated to 200° C. (range of ambient to 300° C.)to assist in keeping the gold wire 101 in a malleable state. The diefixture is also heated to 200° C. (range of ambient to 300° C.) to avoidwire cooling during the bonding process. The die fixture is made ofTeflon-coated aluminum. As shown in FIG. 1, a vacuum cavity or vacuumplate 103 holds the die 104 in position on the fixture during thebonding process.

In step 3, the bonding machine lowers the capillary 100 to the surfaceof a bonding pad 105 and applies high pressure (range of 30-250 grams)to the trapped gold ball 106 along with ultrasonic vibration at thecapillary tip 102. The capillary tip 102 is flat, with a 4-mil insidediameter and an 8-mil outside diameter. The ball 106 is flattened toabout a 3-mil height and a 6-mil diameter. Ultrasound is driven throughthe ceramic capillary 100 to vibrate the gold ball 106 and scrub thebonding pad surface. The sound is oriented so that the gold ball 106moves parallel to the die surface. The Hughes ball bonding machine hasthe ability to vary the touch-down velocity, i.e., soft touch-down forbonding GaAs, which is program selectable. The ultrasonic application isalso program selectable.

In step 4, the capillary 100 is withdrawn from the die surface 104,extending the gold wire 101 as the head is raised. The nitrogen drag isleft off and the capillary is raised to a height to allow enough goldwire to form the flying lead, a tail length for the next flying lead,and a small amount of clearance between the tail length and thecapillary tip 102. The Hughes ball bonder device is capable of selectingthe height that the capillary tip can move up to a height ofapproximately 0.750 inch.

In step 5, an automatic notching mechanism 115 moves into the area ofthe extended gold wire 101 and strikes both sides of the wire with steelblades. This is essentially a scissor action which cuts most of the waythrough the gold wire 101, forming a notch 107. The notch 107 is made 27mils above the surface of the die. The notching mechanism has been addedto the Hughes ball bonder for the precise termination of the flyingleads. The Hughes ball bonder has been modified to measure and displaythe notch mechanism height. The activation signal for the notchmechanism is provided by the Hughes ball bonder system for the properactivation during the sequence of ball bonding The flying lead length isadjustable from between 0.0 mils to 50.0 mils. It will be appreciated bythose skilled in the art that the notching function can be accomplishedwith a variety of mechanisms such the scissor mechanism disclosed above,a hammer-anvil system, and a variety of other mechanisms that merelynotch or completely sever the wire 101.

In step 6, clamp 108 closes on the gold wire 101 above the capillary 100and the head is withdrawn until the gold wire breaks at the notchedpoint. This stretching process serves several useful purposes.Primarily, the gold wire is straightened by the stretching force andstands perpendicular to the die surface. In addition, the bond isnon-destructively pull-tested for adhesion at the bonding pad. The lead101 is terminated at a 27-mil height above the die surface 104 in thepreferred embodiment. At the end of step 6, the capillary head for thebonding mechanism is positioned over a new bonding pad and the processof steps 1-6 begin again. The bonding wire 101 is partially retractedinto the capillary once again, and the clamps are closed, as shown instep 1, so that a new ball may be formed by the EFO.

The die positions are roughly determined by the loading positions in thevacuum fixture. The Hughes automatic bonding machine is able to adjustthe X-Y table for proper bonding position of the individual die. Anangular correction is automatically made to adjust for tolerance inplacing the die in the vacuum fixture. This is done through a visionsystem which recognizes the die pad configurations. Using the modifiedHughes automatic bonding machine with the current bonding technique, aminimum bonding rate of 2 die pads per second is possible.

Circuit Board Construction

Once the gold bonding leads are attached to the integrated circuit chipor die, the die is ready to be attached to the circuit board. As shownin FIG. 3, the bonding pattern of the integrated circuit die 104 matchesthe plated hole pattern on the circuit board 110. For example, the topview of integrated circuit die 104 in FIG. 3 shows the bonding pad 105in the upper right corner. The circuit board 110 shown in FIG. 3 shows acorresponding plated hole 111 which is aligned to receive the bondinglead from bonding pad 105 when circuit board 110 is placed overintegrated circuit 104 and the flying leads are inserted into the holepattern on the circuit board. Thus, each bonding pad of integratedcircuit 104 has a corresponding plated hole on circuit board 110 alignedto receive the flying leads.

The circuit board assembly operation begins with the die insertion inthe circuit board. The circuit board is held in a vacuum fixture duringthe insertion process. This is to make sure that the board remains flat.Insertion can be done by hand under a binocular microscope or productionassembly can be done with a pick-and-place machine.

Referring to FIG. 4, the circuit board 110 with the loosely placed die104 is mounted on an aluminum vacuum caul plate (lower caul plate) 113.Steel guide pins (not shown) are placed in corner holes of the circuitboard to prevent board motion during the assembly operation. A second(upper) caul plate 112 is then placed on the top side of the circuitboard populated with chips to press against the tops (non-pad side) ofthe chips 104. The sandwich assembly comprising the circuit circuitboard, the chip and the caul plates is then placed in a press andpressure is applied to buckle and expand the gold leads 101 in theplated holes 111 of the circuit board.

The side view of the sandwiched circuit board 110, integrated circuitchip 104, and caul plates 112 and 113 in FIGS. 4 and 5 illustrates theposition of the gold leads 101 before and after the pressing operation,respectively. In the preferred embodiment there is a 7-mil exposure ofgold lead 101 which upon compression will buckle and expand into theplated hole 111 of the circuit board 110. The 3-mil diameter wire 101 ina 5-mil diameter hole 111 means the initial fill is 36 percent of theavailable volume. After pressing, the fill has increased to 51 percentas a result of the 7-mil shortening of the gold lead 101. As shown ingreater detail in FIGS. 5 and 5a, the lead typically buckles in two ormore places, and these corners are driven into the sides of the platedhole 111 of the circuit board. The assembly is completed in one pressingoperation. The circuit board 110 can now be removed from the press withthe integrated circuit chip 104 securely attached and electricallybonded to the plated holes of the circuit board.

FIG. 6 shows a broader view of the circuit board press which is used toattach the integrated circuits to the printed circuit board. The uppercaul plate 112 is a Teflon-coated seating caul plate which is alignedthrough alignment pins 114 with the circuit board 110 and the lower caulplate 113 which is vacuum caul plate to hold the circuit board flatduring the pressing process. The alignment pins 114 are used to preventthe printed circuit board 110 from sliding or otherwise moving duringthe pressing process. A seating force is applied to the top of uppercaul plate 112 which forces the excess flying lead material into theplated holes of printed circuit board 110. Thus, integrated circuits 104are mechanically and electrically bonded to printed circuit board 110.

It will be appreciated by those skilled in the art that many variationsof the above-described pressing operation can be used which results inthe same or equivalent connection of the flying leads to the PC boards.For example, the flying leads of the chips could be completely insertedinto the through-plated holes of the PC board prior to the pressingoperation with the excess gold leads protruding out the opposite side.The first caul plate could then be used to hold the chip onto the PCboard while the second caul plate is used to compress the leads into theholes.

Module Assembly Construction

A sandwiched assembly of printed circuit boards populated withintegrated circuit chips is interconnected using a technique similar tothat used in bonding the integrated circuit chips to the circuit boards.As is more fully described below, soft mold wires are inserted throughaxially aligned plated holes between layered circuit boards which arecompressed using caul plates to partially fill the plated holes with thesoft gold wires to form an electrical connection substantiallyperpendicular to the planar surfaces of the printed circuit boards.

FIG. 7 is an example of a printed circuit board hole pattern for thetype of circuit boards used in the Cray-3 computer manufactured by theassignee of the present invention. In the preferred embodiment of thepresent invention, each circuit board provides 16 plated hole patternsfor the acceptance of 16 integrated circuits having flying leads. The 16integrated circuits are attached to each of the circuit boards of thetype found in FIG. 7 through the pressing process previously describedfor circuit board assembly. Caul plates of a size slightly larger thanthe circuit boards of the type shown in FIG. 7 are used during thepressing process to attach the integrated circuit chips to the circuitboards. Each plated hole pattern on circuit board 110 of FIG. 7corresponds to the hole pattern disclosed in FIG. 3. Each corner ofcircuit board 110 includes four plated via holes which are used todistribute power and are used for alignment during the pressingoperation.

In the preferred embodiment of the present invention, 16 of the circuitboards 110 shown in FIG. 7 are arranged in a module assembly 200 of thetype shown in FIG. 8. The circuit boards 110 are arranged in a 4×4matrix on each level of the module. There are four levels of the modulein which circuit boards are stacked, thus created an X-Y-Z matrix of4×4×4 circuit boards. This results in 64 circuit boards for each moduleassembly 200 which in turn results in 1,024 integrated circuit chips permodule assembly.

A module assembly is 4.76 inches wide, 4.22 inches long, and 0.244 inchthick. A top view of a module assembly is shown in FIG. 8. At one edgeof the module assembly are four power blades 201a-201d. Each of thepower blades is one example of means for applying electrical power to apower plate to which the power blade is connected. These machined metalblades are both the mechanical connection to the cabinet into which themodule assemblies are placed and the electrical connection to the powersupplies, as a result of fitting into an electrical power inputconnector. At an opposite edge of the module assembly are 8 signal edgeconnectors 202a-202h. These connectors form the communication paths tothe other module assemblies within the machine.

Electrical communication between the integrated circuit chips of eachboard 110 is accomplished by means of the prefabricated foil orconductor patterns on the surface and buried within each circuit board.The electrical communication between circuit boards 110 is between twologic boards or plates sandwiched in the center of the module assembly.Communication between the circuit boards and the logic plates is throughgold post jumpers along the Z-axis direction perpendicular to the planarsurface of the circuit boards and the module assembly. The z-axis jumperwires are used for distribution of electrical communication signals andpower distribution. The Z-axis jumpers are placed in any of the area oncircuit boards 110 that is not occupied by an integrated circuit.

Due to the amount of force required to compress the jumpers along theZ-axis of the module assembly, the jumpers are compressed for a 4-boardstack at one of the 16 locations on the module 200 at a single time. Theorder in which the circuit boards are compressed is shown in FIG. 8 inthe lower left corner of each circuit board stack 110. Sixteen separatepressings are performed to compress the gold Z-axis jumpers for onemodule 200.

FIG. 9 shows a side sectional view of a module assembly The assembly 200is constructed as a sandwich comprising four layers of circuit boards,two layers of circuit board interconnect layers, and several layers ofsupport framing material. FIG. 9 depicts a completely assembled moduleassembly with the exception of the single edge connectors, which havebeen omitted for purposes of this discussion. The assembly 200 inapplication is stacked with other assemblies in a fluid cooling tank andpositioned so that the planar surface of the module assembly is stackedin a vertical direction. Thus, in application, the view of the circuitboard assembly 200 of FIG. 9 is actually a top-down look at the modulein application. A type of cooling apparatus suitable for cooling thecircuit board module assemblies of the present invention is described inU.S. Pat. No. 4,590,538 incorporated herein by reference.

Eight cooling channels 230 are provided at the outer sections of themodule assembly to allow the vertical rise of cooling fluid through themodule assembly to remove the excess heat produced by the integratedcircuits in operation. Heat transfer occurs between circuit boards 1 and4 (levels 212 and 221 respectively) and the fluid passing throughchannels 230. There is also heat transfer from the ends of logic jumpers231 to the passing fluid in channels 230. The latter is the primary heattransfer vehicle from circuit boards 2 and 3 (levels 214 and 219,respectively). The power plates at levels 210 and 223 are spaced fromthe board stacks to form the fluid channels. Spacing is accomplishedwith acrylic strips 203 which are held in place by the power jumpers232.

The module assembly 200 as shown in FIG. 9 depicts at 201, the one ofthe four power blades 201d shown to the left as shown in FIG. 8. Theouter plates shown as layers 210 and 223 (FIG. 9) are power distributionplates which connect to the four power blades (FIG. 8) and are used todistribute electrical power throughout the module for powering theintegrated circuits. The connection between the integrated circuits andthe power plates is by Z-axis power jumpers which are described in moredetail below.

As was previously described, each module assembly consists of 16 boardstacks. Each board stack consists of four circuit boards. The side edgeview of the module assembly shown in FIG. 9 shows four board stacksexposed in a cut-away view. The four circuit board levels are labeledNos. 212, 214, 219 and 221. Electrical signal communication betweenthese boards is via two logic plates labeled 216 and 217. These platesare in the center of the module assembly and divide the board stacks inhalf. Communication between circuit boards 212, 214, 219 and 221 andlogic plates 216 and 217 is via gold post jumpers or logic jumpers 231in the Z-axis direction (relative to the X-Y axes lying on the planarsurface of the circuit boards and logic plates). The logic plates aswell as the circuit boards contain electrical interconnecting platedwiring conductor patterns in the X-Y direction, and the Z-directioninterconnect is thus performed by the logic jumpers.

The integrated circuits 104 are shown in FIG. 9 as the rectangles atlevels 213, 215, 218 and 220. The flying leads from these integratedcircuits are attached to circuit boards 212. 214, 219 and 221respectively. Thus, the circuit board assembly of 212 with integratedcircuits at level 213 are assumed to have been previously assembled withthe aforementioned flying lead attachment of integrated circuits tocircuit boards. The spaces between the integrated circuits at levels213, 215, 218 and 220 contain through-plated holes which are axiallyaligned in the Z-axis direction and allow the gold post logic jumpers231 to pass through the various levels of the module. The spaces betweenthe integrated circuits on levels 213, 215, 218 and 220 are filled witha die frame which also contains corresponding axially aligned holes.This is a clear acrylic plate or block the size of the circuit boardsapproximately 10 mils thick. There are relief areas in the die frame forthe integrated circuit packages and for the gold post jumpers which passthrough the board stacks and through the die frames. The purpose of thedie frame is to provide mechanical support for the circuit boards andfor the gold post jumpers.

The jumpers are forced through the board stack under high pressure tointerconnect all of the axially aligned through-plated holes on thecircuit boards and on the logic plates. The gold jumpers 231 are made ofthe same soft gold used in the flying lead connection of the integratedcircuit packages to the circuit boards described above. The soft goldjumpers are compressed through the axially aligned plated holes to formelectrical connections in the Z-axis direction. The die frame preventsthe soft gold of the jumper from escaping into the areas between thecircuit boards adjacent the integrated circuits.

Jumpers 231 in FIG. 9 are similar to the power jumpers 232 also shown inFIG. 9. The power jumpers 232 extend farther than the logic jumpers 231,since they need to connect to power plates 210 and 223 to supply powerto the circuit boards.

FIG. 10 shows a closeup view of a single logic jumper through thevarious levels of assembly 200. This cross-sectional view at FIG. 10 isnot drawn to scale and is offered as an illustration of how the goldleads are compressed within the plated holes of both the circuit boardsand the logic plates. Spacers are used at levels 213, 215, 218 and 220to prevent the gold jumper leads from expanding into the spaces betweenthe circuit boards. Buried plated interconnect or surface interconnecton circuit boards and logic plates form the interconnection between thelogic jumpers and the plated holes for the flying leads of integratedcircuits. Logic or electrical communication between integrated circuitsand the outside world is achieved therefrom. Insulating openings such asthe axially aligned holes in the insulated die frame spacers are alsoprovided in the circuit boards and logic boards for the jumpers to pasthrough to achieve electrical communication through a board withoutelectrical connection to that board whenever such an electrical path isdesired between two or more boards which are not adjacent in theassembly. This situation is illustrated by the power jumpers 232 passingthrough the logic boards 216 and 217, as shown in FIG. 9, but may alsooccur when one logic jumper 231 passes through one of the circuit boardsand makes electrical contact with an adjacent circuit board. It will beappreciated by those skilled in the art that power jumpers will appearsimilar to the logic jumpers shown in FIG. 10, except that the powerjumpers extend into the power plates of the assembly 200 and aresomewhat larger in diameter.

Gold Post Jumper Installation

The module is assembled in two steps. The first step combines thecircuit board stacks with the logic plates. This step is repeated 16times for a module (once for each board stack). The second step connectsthe power plates and the module power blades. Both steps are describedbelow.

The board stacks are assembled to the logic plates in two pressingoperations. These pressing operations are shown in FIGS. 11 and 12. Thepressing operation shown in FIGS. 13 and 14 presses the power jumpersthrough the assembly to form the necessary interconnect between thecircuit board and logic plate layers and the power plate levels.

The four circuit boards (CB), the four die frames, (DF) and the twologic plates are stacked on a metal caul plate with guide pins throughthe corner power jumper holes as shown from the side view of FIG. 11.This is in preparation for the first pressing operation. There is anassembly die frame spacer on the lower caul plate below the firstcircuit board. There is another assembly die frame spacer on the top ofthe stack just below the stamp caul plate, which is removed before thefirst pressing.

Soft gold post jumpers are then loaded into the stack in the positionswhere the jumpers are desired. These gold posts are in the preferredembodiment 5 mils in diameter and 192 mils long. The top assembly dieframe spacer is removed and is replaced with the stamp caul plate. Theassembly is then placed in a press and the jumpers are compressed suchthat the exposed 10 mils of the logic jumpers are compressed into thestack assembly. In this pressing operation, the 10 mils of the exposedgold post at the top of the stack assembly are compressed into theassembly and the gold posts expand in the jumper cavity to a nearly 100percent fill. Excess gold is forced into a nail head configuration onthe top of the outside circuit board. The assembly in FIG. 11 shows thestamp caul plate on the outer surface of circuit board 4 with the topassembly die frame spacer removed.

The pressing operations shown in FIGS. 11 and 12 are accomplished usinglevelers on the outer surfaces of the logic plates to ensure an evenpressing operation. The guide pins are placed at various points throughthe power jumper holes along the logic plates to ensure that the circuitboards and logic plates do not move during the pressing operation.

FIG. 12 shows the second pressing operation. The board stack shown inFIG. 11 is turned over with the caul plates reversed In the secondpressing operation, the top assembly die frame spacer on the top side ofthe stack is now removed and another press cycle occurs, pressing theremaining 10 mils of the exposed jumper into the stack. The reason forthe two-sided pressing operation is that the soft gold bindssufficiently in the jumper cavity so that it is not possible to make areliable connection through the entire stack from one side only. Thenumber of pressing operations of course would vary with the number oflevels in the sandwiched assembly. In smaller (thinner) assemblies,one-sided pressing is possible.

With board stacks having a larger number of levels of circuit boards,logic plates and chips, longer logic jumpers and power jumpers may beused to interconnect along the Z-axis, however, more pressing operationsmay be required. For example, in an alternate embodiment of the presentinvention, four pressing operations may be required for logic jumpersThe first pressing operation would be similar to that shown in FIG. 11,except that two 10-mil spacers would be placed at the bottom of theboard stack and two 10-mils spacers placed at the top of the boardstack. The first pressing operation would press 10 mils of the logicjumpers into the board stack after the removal of the top spacer Thesecond step would start with the removal of the second spacer on thetop, and a second pressing operation would occur. The third pressingoperation would begin with the board stack flipped over and the top10-mil spacer removed for the third pressing step. The last pressingstep would begin with the removal of the final 10-mil spacer and a finalpressing operation would begin. In this application, 20 mils of exposedgold jumper could be pressed into a thicker board stack.

Power plates and module power blades are added to the partial moduleassembly in a manner similar to the pressing operation for theindividual circuit board stacks. In this case, instead of a stamp caulplate of approximately the size of a single circuit board, caul platesthe size of the entire assembly are used to press all of the powerjumpers on the entire module assembly, as shown in FIG. 13. The powerjumpers are loaded and pressed in a four-step cycle as described abovefor the logic jumpers of a single circuit board stack assembly. The goldposts for this power jumper pressing operation are 14 mils in diameterand 284 mils long. The module power blades are attached as a last stepby pressing gold posts or aluminum posts into cavities in the machinedpower blades, as shown in the final step of FIG. 14.

Those of ordinary skill in the art will recognize that other types oflead bonding processes may be substituted for the ball bonding processfor flying leads described herein. Also, other types of malleableelectrically conductive metals may be used in place of the soft golddescribed herein. In addition, the pressing process causing the gold toexpand or buckle within the plated holes may be performed without havingthe gold leads protrude from the circuit board. Compression fingerscould be axially aligned with the plated holes in order to compress thegold leads within the plated holes without having the leads protrudingbefore the process is begun.

While the present invention has described connection with the preferredembodiment thereof, it will be understood that many modifications willbe readily apparent to those of ordinary skill in the art, and thisapplication is intended to cover any adaptations or variations thereof.Therefore, it is manifestly intended that this invention be limited onlyby the claims and the equivalents thereof.

What is claimed is:
 1. A three-dimensionally electrically interconnectedcircuit board module apparatus, comprising:a plurality of circuit boardscoplanar in a plane defined by an x axis and a y axis, each of thecircuit boards located along a z axis, each circuit board having aprefabricated conductor pattern, a plurality of unpackaged integratedcircuit chips mounted to the conductor pattern of at least one circuitboard, a plurality of power through-plated holes electrically connectedto the conductor pattern of each circuit board, and a plurality of logicthrough-plated holes electrically connected to the conductor pattern ofeach circuit board; at least one power plate coplanar with and locatedalong the z axis from said circuit boards and having a prefabricatedconductor pattern for distributing electrical power, a plurality ofthrough-plated holes electrically connected to the conductor pattern ofthe power plate, at least two of the through-plated holes on the powerplate located substantially in respective axial alignment along the zaxis with said power through-plated holes on said coplanar circuitboards; at least one logic board coplanar with and located along the zaxis from said circuit boards and having a prefabricated conductorpattern for communicating electrical signals therealong, a plurality ofthrough-plated holes electrically connected to the conductor pattern ofthe logic board, at least two of the through-plated holes on the logicboard located substantially in respective axial alignment along the zaxis with said logic through plated holes on said coplanar circuitboards; a plurality of electrically conductive z-axis power jumpers,each power jumper electrically connected to a through-plated hole onsaid power plate and an axially aligned power through-plated holes onsaid circuit boards; a plurality of electrically conductive z-axis logicjumpers, each logic jumper electrically connected to a through-platedhole on said logic board and to an axially aligned logic through-platedhole on said circuit boards; a power input means for applying electricalpower to the conductor pattern of said power plate; and a spacer meansfor maintaining each of said circuit boards, said power plate and saidlogic board in a spaced, fixed, and coplanar relationship located alongthe z axis.
 2. The apparatus according to claim 1 wherein said powerinput means comprises at least one power blade dimensioned to fit intoan electrical power-input connector, said power blade fixedly secured tosaid circuit board module apparatus and in electrical contact with eachsaid power plate prefabricated conductor pattern.
 3. The apparatusaccording to claim 1 wherein said logic board contains at least oneopening having at least one of said z-axis power jumpers passing throughsaid opening.
 4. The apparatus according to claim 1 wherein at least oneof said circuit boards contains at least one opening having at least oneof said z-axis logic jumpers passing through said opening.
 5. Theapparatus according to claim 1 wherein at last one of said z-axis logicjumpers electrically connects to a plurality of axially aligned logicthrough-plated holes of the circuit boards.
 6. The apparatus accordingto claim 1 wherein at least one of said circuit board contains at leastone opening having at least one of said z-axis power jumpers passingthrough said opening.
 7. The apparatus according to claim 1 wherein atleast one of said z-axis power jumpers electrically connects to aplurality of axially aligned power through-plated holes of the circuitboards.
 8. The apparatus according to claim 1 wherein at least onejumper is a single elongated continuous deformable electrical conductorwhich connects to each axially aligned through-plated hole by mechanicaldeformation within the through-plated hole to establish an electricaland mechanical connection with the through-plated holes.
 9. Theapparatus according to claim 8 wherein all of the jumpers connect toeach axially aligned through-plated hole by mechanical deformation. 10.The apparatus according to claim 9 wherein said deformed jumpers andsaid spacer means retain said circuit boards, said power plate and saidlogic board in said spaced, fixed, and coplanar relationship.
 11. Theapparatus according to claim 9 wherein the deformation of the jumpers isa compression of the length of the single elongated electricalconnector.
 12. The apparatus according to claim 9 wherein eachintegrated circuit chip includes a plurality of elongated leads attachedthereto by which signals are applied to and received from said chip, andeach chip is electrically and mechanically mounted to the conductorpattern by mechanical compression of the length of the leads withinthrough-plated holes electrically connected to the conductor pattern ofa circuit board.
 13. A circuit board module apparatus having electricalconnections in the x, y, and z axis directions, comprising:an array of aplurality of circuit boards stacked in the z axis direction and coplanarin the x and y axis directions, each circuit board having aprefabricated conductor pattern, a plurality of unpackaged integratedcircuit chips mounted to the conductor pattern of at least one circuitboard, a plurality of power through-plated holes electrically connectedto the conductor pattern of each circuit board, and a plurality of logicthrough-plated holes electrically connected to the conductor pattern ofeach circuit board; at least one power plate coplanar with and locatedalong the z axis direction from said circuit boards and having aprefabricated conductor pattern for electrically distributing power, aplurality of through-plated holes electrically connected to theconductor pattern of the power plate, at least two of the through-platedholes on the power plate located substantially in respective axialalignment in the z axis direction with said power through-plated holeson said coplanar circuit boards; at least one logic board coplanar withand located along the z axis direction from said circuit boards andhaving a prefabricated conductor pattern for communicating electricallogic signals, a plurality of through-plated holes electricallyconnected to the conductor pattern of the logic board, at least two ofthe through-plated holes on the logic board located substantially inrespective axial alignment in the z axis direction with said logicthrough-plated holes on said coplanar circuit boards; a plurality ofelectrically conductive z-axis power jumpers, each power jumperelectrically connected to a through-plated hole on said power and anaxially aligned power through-plated hole on said coplanar circuitboards; a plurality of electrically conductive z-axis logic jumpers,each logic jumper electrically connected to a through-plated hole onsaid logic boards and to an axially aligned logic through-plated hole onsaid coplanar circuit boards; a power input means for applyingelectrical power to the conductor pattern of said power plate; a spacermeans for creating and maintaining a three dimensional circuit boardmodule apparatus with said circuit board array, said power plate, andsaid logic board in a spaced, fixed, and superposed coplanarrelationship; and said spacer means defining in conjunction with atleast two of said boards or plates a fluid cooling channel forconducting non-electrically conducting liquid within said channel toremove heat from said circuit board module apparatus.
 14. The apparatusaccording to claim 13 wherein said power input means comprises at leastone power blade dimensioned to fit into an electrical power-inputconnector, said power blade fixedly secured to said circuit board moduleapparatus and in electrical contact with each said power plateprefabricated conductor pattern.
 15. The apparatus according to claim 13wherein at least one of said z-axis logic jumpers extends into thecooling channel to conduct heat from a circuit board to the fluid in thechannel.
 16. The apparatus according to claim 13 wherein said logicboard contains at least one opening having at least one of said z-axispower jumpers passing through said opening.
 17. The apparatus accordingto claim 13 wherein at least one of said circuit boards contains atleast one opening having at least one of said z-axis logic jumperspassing through said opening.
 18. The apparatus according to claim 13wherein at least one of said z-axis logic jumpers electrically connectsto a plurality of axially aligned power through-plated holes of thecircuit boards.
 19. The apparatus according to claim 13 wherein at leastone of said circuit boards contains at least one opening having at leastone of said z-axis power jumpers passing through said opening.
 20. Theapparatus according to claim 13 wherein at least one of said z-axispower jumpers electrically connects to a plurality of axially alignedpower through-plated holes of the circuit boards.
 21. The apparatusaccording to claim 13 wherein at least one jumper is a single elongatedcontinuous deformable electrical conductor which connects to eachaxially aligned through-plated hole by mechanical deformation withineach through-plated hole to establish an electrical and mechanicalconnection with the through-plated holes.
 22. The apparatus according toclaim 21 wherein all of the jumpers connect to each axially alignedthrough-plated hole by mechanical deformation.
 23. The apparatusaccording to claim 22 wherein said deformed jumpers and said spacermeans retain said circuit boards, said power plate and said logic boardin said spaced fixed, and coplanar relationship.
 24. The apparatusaccording to claim 22 wherein the deformation of the jumpers is acompression of the length of the single elongated electrical connector.25. The apparatus according to claim 22 wherein each integrated circuitchip includes a plurality of elongated leads attached thereto by whichsignals are applied to and received from said chip, and each chip iselectrically and mechanically mounted to the conductor pattern bymechanical compression of the length of the leads within through-platedholes electrically connected to the conductor pattern of a circuitboard.
 26. A three-dimensionally electrically interconnected circuitboard module apparatus, comprising:a plurality of at least three boardsoriented generally coplanarly in a plane defined by an x axis and a yaxis, each of the boards located along a z axis, each board having aprefabricated electrical conductor pattern, one of the boards being acircuit board having at least one unpackaged integrated circuit chipmounted to the conductor pattern thereof, one of the other boards beinga power board for conducting electrical power to said module apparatus,and one of the other boards being a logic board; a plurality ofthrough-plated holes formed in each board and electrically connected tothe conductor pattern of each board, at least some of the through-platedholes in two of the adjacent boards being axially aligned along the zaxis; an electrically conductive z-axis power jumper electricallyconnecting a through-plated hole on the power board with an axiallyaligned through-plated hole on the circuit board to conduct electricalpower from the power board to each integrated circuit chip mounted onthe conductor pattern of the circuit board; and an electricallyconductive z-axis logic jumper electrically connecting a through-platedhole on the logic board and to an axially aligned through-plated hole onthe circuit board to conduct logic signals from each integrated circuitchip mounted on the conductor pattern of the circuit board.
 27. Theapparatus according to claim 26 wherein at least one jumper is a singleelongated continuous deformable electrical conductor which connects toeach axially aligned through-plated hole by mechanical deformationwithin the through-plated hole to establish an electrical and mechanicalconnection with the through-plated holes.
 28. The apparatus according toclaim 27 wherein all of the jumpers connect to each axially alignedthrough-plated hole by mechanical deformation.
 29. The apparatusaccording to claim 28 further comprising:spacer means for maintainingthe boards in a spaced, fixed, and coplanar relationship separated alongthe z axis.
 30. The apparatus according to claim 29 wherein saiddeformed jumpers and said spacer means retain said boards in saidspaced, fixed, and coplanar relationship.
 31. The apparatus according toclaim 29 wherein at least one jumper extends into the cooling channel toconduct heat from a circuit board to the fluid in the channel.
 32. Theapparatus according to claim 31 wherein one of said boards contains atleast one opening having at least one of the jumpers passing throughsaid opening.
 33. The apparatus according to claim 28 wherein thedeformation of the jumpers is a compression of the length of the singleelongated electrical connector.
 34. The apparatus according to claim 28wherein each integrated circuit chip includes a plurality of elongatedleads attached thereto by which signals are applied to and received fromsaid chip, and each chip is electrically and mechanically mounted to theconductor pattern by mechanical compression of the length of the leadswithin through-plated holes electrically connected to the conductorpattern of a circuit board.
 35. The apparatus according to claim 26wherein one of said boards contains at least one opening having at leastone of the jumpers passing through said opening.
 36. The apparatusaccording to claim 26 further comprising:spacer means for maintainingthe boards in a spaced, fixed, and coplanar relationship separated alongthe z axis, said spacer means defining in conjunction with at least twoof said boards a fluid cooling channel for conducting non-electricallyconducting fluid to remove heat from said circuit board.